Something that's enigmatic is tough to figure out. It's puzzling and even mysterious, like those weird secret college societies, Mona Lisa's smile or the New York Times crossword.
It's no mystery where the adjective enigmatic comes from: It's rooted in the Greek word for riddle. Something that's enigmatic is obscure, unclear and not an easy nut to crack. Translating the Rosetta Stone, with its ancient Egyptian hieroglyphs and mysterious foreign writings, was certainly an enigmatic challenge for the archaeologists that found it.
